PLANTING 
83 
half-year of gardening into three planting periods : early, mid- 
summer, and late. The early spring planting would include 
lettuce, carrots, radishes, onions, and early peas, to be fol- 
lowed by beans and corn ; the midsummer planting calls for 
cabbage, tomato plants, and beets, and also for carrots again ; 
the autumn planting includes such vegetables as celery, cab- 
bage, and cauliflower, all of which will be set out as small 
plants, with the addition of such seeds as can withstand the 
hardships of winter. As a rule, do not replace a plant by one 
which takes out of the soil its food materials in about the 
same proportion ; plan rather to replace it by a plant which 
will use elements that have not yet been largely drawn upon. 
The food in the soil can thus be made to go a great deal 
farther. A few general rules will save many a mistake. To 
begin with, it should be remembered that, classed according 
to diet, such vine plants as the cucumber and squash belong 
in one group ; that the root crops, together with potatoes and 
onions (neither of which, of course, is a true root), belong in 
another ; while the seed crops, beans and peas, together with 
the cabbage tribe and tomatoes, make a third. All those that 
belong in one of these groups have been found to use up the 
essential food elements in about the same proportions. This 
gives a simple basis for the rules of crop rotation. Cabbage 
consumes a great amount of nitrogen ; so does corn. Corn 
and potatoes, on the other hand, draw heavily upon the sup- 
ply of potash. Beans and peas, however, actually enrich the 
soil with proteids, which, as we know, are so valuable for 
the nitrogen they contain. 
The subject of crop rotation is one that requires serious con- 
sideration. This deals with the system by which a carefully 
arranged sequence of different crops is grown advantageously 
upon the same piece of land. Such a scheme is directly 
opposed to the old-fashioned one-crop system, by which 
